Wireless communication is a rapidly developing technology in the modern field of electronic communication. For instance, cellular communication systems have experienced exponential growth in recent decades, serving billions of users worldwide. In many aspects of modern social and business interaction, mobile phones have become an essential part of life in both industrial and developing segments of the world.
Mobile phones and related mobile electronic communication devices provide great convenience to consumers. As a result, wireless networks have begun gradually replacing wired networks in many homes, businesses and campuses worldwide. New applications for these devices, including sensor networks, automated highways and factories, etc., have emerged from the varied research and development in the overall field of wireless communication. Though the expansion of wireless communication and related applications has been explosive, many technical challenges remain in designing robust wireless networks that deliver sufficient performance and quality for ongoing developing applications.
Conventionally, wireless networks provide significant advantages over wired electronic communication, including convenience and portability of mobile phones, and the rapidly increasing processing technology of mobile phones. However, physical wired communication has greater bandwidth enabling greater transmission rates. One challenge for wireless networks in competing with physical wired networks is increasing bandwidth of wireless communication. Another challenge for wireless communication is multi-path fading that causes mis-detection of received signals due to variations in signal power.
Various recent advancements in wireless technology have provided improvement in data rates and detection probability for wireless communication. For instance, multiple-input, multiple-output (MIMO) systems have been developed to improve spectral efficiency of wireless communication through spatial multiplexing. Robustness and reliability of wireless links are also improved by space-time coding and beamforming. Generally speaking, MIMO systems and spatial multiplexing techniques are possible with the advent of multiple radio frequency antennas into transmitters and receivers.
A widely accepted technique for mitigating negative consequences of fading channels for wireless communication is diversity technology. In many wireless networks, however, electronic devices may not be able to support multiple antennas due to size, complexity, cost, or related constraints. In this case, the benefit of MIMO communication cannot be realized for conventional devices and systems. Rather, these systems and devices commonly require alternative techniques to overcome physical hardware limitations to achieve diversity.
Relatively speaking, cooperative wireless communication is new approach in providing diversity gain to increase wireless network capacity. Cooperative communication facilitates resource sharing among single-antenna user equipment, where respective user devices can inter-communicate achieving a virtual multi-antenna array comprising multiple single antenna devices. A virtual MIMO system can be established in this fashion that can accomplish diversity transmission and diversity reception with a multi-antenna base station. Although a single antenna user equipment does not by itself achieve diversity according to this technique, by relaying signals received from another user equipment or a base station, an additional version of transmitted information can be received at a destination, achieving spatial diversity.
In cooperative communication, signal relays or signal forwarding can be performed in two general categories, including hard forwarding and soft forwarding. Hard forwarding is generally considered a conventional one, which employs hard-decision bits in cooperation. Hard-decision bits are generated, at a high-level perspective, by analyzing signal information and determining a fixed set of possible values for the signal information (generally a one or a zero in the binary context). In contrast, soft forwarding involves analyzing the signal information and generating a range of information from the signal information, for instance between the fixed set of possible values, and forwarding this range of information to a destination device.
By providing additional information about signal information, soft forwarding tends to improve end-to-end performance for wireless communication, particularly for noisy or otherwise poor wireless channels. However, soft forwarding increases complexity and processing overhead, in some cases prohibitively so. Accordingly, existing soft forwarding techniques can be limited in their applications in real-world wireless communication systems.
The above-described deficiencies of conventional wireless communication systems are merely intended to provide an overview of some of the problems of current technologies, and are not intended to be exhaustive. Other problems with the state of the art, and corresponding benefits of some of the various non-limiting embodiments described herein, may become further apparent upon review of the following detailed description.